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Old 09-14-2018, 11:13 PM   #1
jocko
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2001-2002 Allison vs 4L80E in a K2500

Quick question - I'm a 4L80E fan, but have no experience with an Allison 5-speed. While I'm assuming the optional Allison has a higher torque rating, the 4L80E is no slouch. Am mostly concerned with longevity. Interested in your thoughts for those that have had both or either. My puny 4L60E in my 1/2 ton is on its third life. Am looking around at 01-02 2500HDs and am curious about teh Allisons - am finding more for sale than I thought I would.

And does anyone know the Allison gear ratios handy?

Also, I "thought" they were only available from the factory behind a big block or a diesel, but I have seen some listed on 6.0L trucks that are for sale. Was that an option?
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Old 09-14-2018, 11:25 PM   #2
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Re: 2001-2002 Allison vs 4L80E in a K2500

I have never seen an Alison behind a 6.0L. I have one behind my 8.1L in my 2001 Silverado and I love it for towing. Truck has 200 000 kilometres on it now and still works fine. Not sure how many miles that is. . I have never had a 4l80 so I can't compare but those I hear are pretty good transmissions as well.
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Old 09-14-2018, 11:51 PM   #3
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Re: 2001-2002 Allison vs 4L80E in a K2500

Thanks Chewy
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Old 09-15-2018, 10:26 AM   #4
95 S_Trucker
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Re: 2001-2002 Allison vs 4L80E in a K2500

The only trucks that got the Alison were duramax and 8.1.

They were never offered behind a 6.0. People are falsely advertising or they don't know what they have.
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Old 09-15-2018, 10:12 PM   #5
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Re: 2001-2002 Allison vs 4L80E in a K2500

thx Trucker, that's kinda what I was thinkin. Thanks guys.
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Old 09-25-2018, 12:17 AM   #6
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Re: 2001-2002 Allison vs 4L80E in a K2500

I had the Allison behind the 8.1L in my 2002 K2500. I was good for towing but the gas mileage sucked. I think I got around 6-8 MPG when I had my boat and camper hooked up. I moved up to the Duramax with the Allison and WOW....there is a night and day difference. I can tow anything almost effortlessly now and the MPG is about 15 with everything connected. Oh and I forgot to mention, I can use my cruise control in my Duramax where I couldn't in the 2002 with the 8.1. RPM's would go through the roof. Just my 2 cents and experience.
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Old 09-25-2018, 09:51 PM   #7
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Re: 2001-2002 Allison vs 4L80E in a K2500

Thanks very much for the info!!
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